


The Mysterious Neighbor

by Fearcrow



Category: Undertale (Video Game)
Genre: Alternate Universe - Swapfell (Undertale), Alternate Universe - Underfell (Undertale), Alternate Universe - Underswap (Undertale), Childhood Trauma, Cussing, Echo (Echofell G!sans), Ecto-Penis (Undertale), Ecto-Tongue (Undertale), Freeform, Frisk is female, Green (G!Paps), Implied/Referenced Underage Sex, Male Chara (Undertale), Multi, Murder, Post-Traumatic Stress Disorder - PTSD, Post-Undertale Pacifist Route, Rape/Non-con Elements, Rave (Echotale Frisk), Reader Is Not Frisk (Undertale), References to Undertale Genocide Route, Sans (Undertale) Remembers Resets, Undertale Genocide Route, Undertale Pacifist Route, Undertale Saves and Resets, g!sans - Freeform, reverse-harem - Freeform
Language: English
Status: In-Progress
Published: 2019-05-09
Updated: 2019-05-23
Packaged: 2020-02-28 18:46:41
Rating: Mature
Warnings: Graphic Depictions Of Violence, Major Character Death, Rape/Non-Con, Underage
Chapters: 2
Words: 2,901
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18762253
Author URL: https://archiveofourown.org/users/Fearcrow/pseuds/Fearcrow
Summary: Sans barely knows you, but you remember him, you remember them all and they not the ones you want to disappear.





	1. A Puzzle Appears in the form of a Human.

Sans couldn’t sleep, he almost always couldn’t sleep, aside from little cat naps here and there. A cat nap on the couch, a cat nap atop the house, a cat nap in a chair in his study. Tonight, he decided to star gaze. He and his crazy “family” had decided to live away from the city, living out in Galaxy Town which was a good four-hour drive to Ebbot and a six-hour drive to New Ebbot. 

Over the past couple days, the house next to them had been bought but no one that he could see had been inside the home or even came out to take a look at it. The sign had been set to “sold” for a while now. 

But when he saw a truck pull up at the dead of night and pull into the parking lot he raised a bone brow. He saw a young female get out of the car looking around. 

Red hair, blue eyes, and wearing a long coat the flayed out behind her when she walked. Boots he could hear on the pavement. He sat up a bit and watched as she moved into the home taking out her key and slipping inside. 

That was the last he saw of the female for days. 

Almost a week went by and then a truck showed up early morning the movers getting out of the truck and unloading everything. He still hadn’t seen the female. But more of his family had stepped out at the commotion as the human males unlocked the door and went inside moving in the furniture. 

They didn’t say anything or really talk to them, just doing their job. Mostly talking amongst themselves. 

That night was a bit different. You finally emerged from your house looking tired shuffling your feet as you went to get the mail and set out the trash. 

When had you left? Sans wasn’t sure, but he nudged Stretch who was up there with him and nodded in your general direction. 

Stretch had been told about the night the neighbor showed up, and just didn’t remerge after that. Now he got a good look at you and when he went to check out your lvl he got this message 

“Name: Don’t pry, att: ????, Def: ????, Lv: ????, Exp: ????, status: The fuck?” 

When he shifted back you were staring up at them looking… panicked? Scared. They watched as you quickly ran back to your home, falling and hurting yourself, but ultimately pushing yourself back upright and running inside closing the door behind you and most likely locking it. 

Stretch looked at Sans and shrugged. “Couldn’t get nothin’ from her.”

Sans sighed, he didn’t want to live next to a human that was racist or speciest let alone a bigot. 

Over the next couple days, the skeletons started looking out for you, but none of them even once saw you. Though, they knew you must be there because sometimes they heard a stereo playing a song, or some movie or show being played. But none could see inside your house since you kept all the blinds closed, blackout curtains drawn shut, hell they didn’t really see any lights turned on. And the idea that you had a job… well they never saw you come out of the house to go to work. You had groceries delivered and in the blink of their eyelights the groceries would be gone, taken inside though none of them had seen you even open the door a tiny crack. 

Most of the edgier skeletons just let you be and even said as much. That is until a month later Sans and Blue saw the classic Toriel with Frisk at their creepy neighbor’s house. Toriel politely knocking on the door and you cracked the door open, then seeing you jumped up hugging her close, it looked like you were shaking… crying maybe? 

Soon enough Toriel, Frisk, and you were inside your house and the door was once again shut. 

Sans stood there blinking he was curious now. Even Blue and Papyrus who were standing there with him were confounded by the sight of what just happened. A few hours later Toriel was back out and Sans was right there. 

“Ey, Tori… so uh, what brings you around here?” 

“I came to visit my child and let her see Frisk again. It’s been so long since I last got to see her. I’m happy she’s doing better… just not better mentally maybe.” Tori smiled at Sans and Frisk nodded her head. 

She started signing to Sans, “Sis, has problems with people in general, and because of it she’s mostly a recluse.” 

Sans nodded his head looking back at the house you lived in then back to Tori. “So, she’s not speciesist?” 

“Stars no Sans, she’s not. But if you want to know about her why not knock on her door and find out more. It would be nice for her if she had more friends.” 

Frisk nodded her head and then Toriel smiled “I have to cut this short. We came by for our visit and now we must return.” 

Sans waved goodbye but then Frisk caught him and signed real quick to him “She remembers…” is all Frisk signed before leaving. 

Sans blinked… what did that mean? But soon he let it go and decided to head back inside. 

It went this way for a while. He noticed as did the others, that you only stepped outside at night, to throw away trash or collect mail or put mail in the mail box. You always ran back to your house like you were afraid. But afraid of what no one could figure that out. 

“Frisk said herself that the neighbor is a recluse, maybe she just has panic attacks easily?” Red stated. 

“Yeah, maybe, she seems so frightened all the time.” Sans stated and Stretch just shrugged.  
“BETTER TO LEAVE HER BE THEN!” Edge huffed, “WE DON’T NEED ANYONE ELSE TO WORRY OVER.”  
/ /  
You needed to move past this, Mom (Tori) stated as much. Frisk even wanted you to get better, but you had problems… Everytime you stepped outside you could swear you heard him, just around the corner, waiting for you. A knife in his hand this time? Or a bat maybe with nails embedded in it ready to beat you to death? 

Maybe he’d gotten more creative. After all the monsters didn’t kill you off, and you always survived. With trembling hands you ran over to the monster skele’s house and put the little package in there then ran back as you could of swore you heard the footsteps behind you. 

There was no one there of course, you had imagined it. You had been careful not to be found. Slamming the door shut you curled up and put your head in your trembling hands and cried silently pleading that you could either just die this time or just be rid of the constant terror. 

/ /  
Black pulled out the mail the next morning and looked at the package. It wasn’t addressed to anyone in particular. He opened it and pulled out the contents. Inside was a drawing of two skeletons he recognized as Stretch and Sans sitting atop the house, Stretch a cigarette in his mouth and Sans staring up at the stars. 

Inside the note was written in almost perfect hand writing. 

“Sorry for being so rude and informal. Mom said you were nice, but I can’t bring myself to say hi. Not yet at least. I hope this finds its way to you both. I hope you like the picture. 

Sincerely,  
Lillie Dreemurr”

Black noted the name, “Dreemurr” so you were adopted by the King and Queen of monsters. Everyone knew that Classic Tori and Classic Asgore got back together. That they had a few more human children now a days. 

It had been a year and a half, but not once had a “Lillie” ever been mentioned before. 

Taking it inside he left it with Stretch. Stretched looked at it and noted the drawing, it was really well done and the note with the name he too raised a bone brow. There was something off… something not right. He hadn’t ever heard of a “Lillie” with any of the Dreemurrs. 

Black didn’t say anything either, he just left the puzzle pieces with Stretch. 

Sighing he stood up and went to ask Papyrus since Sans was at work. Maybe he’d know more. 

But after talking with Papyrus the only thing he got was that the Queen had went back under the mountain after their freedom and had re-emerged with a young woman and no one had seen that female since that day. 

That left an even bigger puzzle piece missing. No one knew who you were, or how long you had been with the Classic Dreemurrs, let alone that you had even been adopted and the only human in the news had been Frisk, no other humans had ever been mentioned. 

So, who were you and what was so special about you that you had been kept a literal secret from both humans and monsters?


	2. Mutt in the House.

**Summary for the Chapter:**

> Mutt is in your house... but why? We may never know.

**Notes for the Chapter:**

> Yes, I'm aware it's a bit short. I wanted a chapter out. I'm packing up and getting ready for a move. I'm still working and my last day of work is the 11th of June and I leave on the 13th of June. So yeah. I'm doing my best here. Thank you all for being patient with me during this transition in my life.

It was late at night, Mutt couldn’t sleep so he had been outside in the backyard smoking when he heard a screen door clack shut. It came from the other yard, the mysterious neighbor’s yard. He could clearly see into the yard since the fence wasn’t high at all and noticed how you were crouched down on the porch staring up at the stars. 

It decided not to bother you, you didn’t seem like you really wanted to be bothered, but he felt weird… like something was off, and he couldn’t put his tongue on it. Just there, far away, yet so tantalizingly close. 

Suddenly he looked up again and you were right there at the edge of the fence. You looked at him, and he could see you… but he knew you, not you, but you yes… it was… why were you here? Then he heard your words, so soft. 

“Olive you Papyrus.” 

His sockets filled with tears, he reached out to you, but you were gone, going back into the house. He broke down. He thought you looked familiar… but no… he had… he…. 

“MUTT THERE YOU ARE YOU LA….” Black stopped seeing the magical tears going down his face as he looked at him. “What’s wrong?” he asked watching his brother. He had rarely ever seen him cry like this and he was a bit… bewildered to say the least. 

Rus took off, running back into the house grabbing up his coat before just leaving, popping out of there go to classic Grillby’s place since Arachne’s was closed. He decided to drink himself into a stupor. 

/ /   
Hours later he popped back in drunk as a skunk and smelling of one too. He laid down to sleep and his dreams turned to nightmares. 

He was running, chasing down a female, a human that had been in the underground. Finally catching you, his clawed boney hand wrapping around your throat as he grasped it a bit tight. He hated this, he didn’t want to hurt you. He loved you. 

“Olive you Papyrus.” The voice whispered as he cried hearing his brothers’ words telling him to end your life so that they could be free. 

Waking up with a start he put his face in his boney hands and felt his Lv flaring as he snakingly went to get his medication he almost always neglected. You looked like her, and yet you weren’t her. He had to know the truth. But he didn’t think he could face you right now. That and you looked scared. But he did notice one thing. You didn’t seem scared of him. No, it was whatever that was out there, you were scared of something that was out there, beyond the safety of your walls he was sure of it.   
/ / 

“AND NOW HE’S AVOIDING ME.” Black was venting to Stretch, why he was venting to Stretch… because out of all them at least Stretch would give some helpful advice. 

Stars knew how Mutt could give him the silent treatment and it always worked, but now he didn’t know what he did wrong. However, Stretch couldn’t figure it out either. And he gave a lazy shrug. 

Black let out a huff and stood up to leave. “AT LEAST… THANK YOU FOR LISTENING.” 

Stretch merely shrugged again “Any time.” And with that he was safe to curl back up and go to sleep. He did vaguely wonder what happened. He only ever saw Mutt give Black the silent treatment if Black pushed him too far. Or gave out too many ridiculous orders. But lately, even Stretch had to admit, Black had been rather well behaved lately. 

/ /   
You listened on the phone as Echo tried to talk you into going out more, do things. That him, Green, G, Chara, and Frisk all cared too much to see you waste away in your house. Alone, afraid. Even offering to come and visit. To keep you company. But you knew what that would lead to. It always happened. He tried to pull you outside. 

“No… no need. I… I’m fine…I’ll get out m..ore. I promise.” You stuttered out and heard a sigh on the other end. 

“Ok… I’ll let ya go then.” And with that you heard the click on the other end. 

Echo had been the sole survivor of his au, G, Green, and Rave had been the sole survivors of their world. All of them, like you had been adopted by Toriel and Asgore taking the last name Dreemurr. Only, you had been a secret to anyone outside of the family. So not a lot knew of you, not even the other copies of them knew. So, you being here, you knew they didn’t like it, but you had been told it would be for the best. 

Frisk pushed for this… and you did feel a bit better, but you still hated going out. You did not want to run into…

/ /   
A week went by and suddenly there was a knock on your door. Your heart stopped, your breath caught in your throat as you looked at the door. You had gone outside in your backyard… what if… what if … “he” found you.

Slowly you approached the door and saw a tall skeleton with a fur lined hoodie, but he was tall. You knew who he was. 

Opening the door, you glanced up at him and smiled. You’re eyes threatening tears. Opening the door wider, you let him then closed it. The minute he was in he wrapped his arms around you and lifted you up hugging you close. 

There was a lot to discuss, he had a lot of questions, and you had the answers. 

/ /   
After that day Mutt had been acting more strangely, not only that there seemed to be a bit more activity at the neighbor’s house than usual lately. Black couldn’t help but notice. The lights in the kitchen were on, he saw glimpses of you; and then he saw Mutt… “THE HELL!” 

Blue was about say ‘language’ when he too looked up and saw Mutt standing in… the mysterious neighbors house. Looks like he was getting water and moving away from the window. Blue jumped up onto the counter and moved trying to get a better view. When he turned back because he couldn’t see any better he found Black was already gone, storming out of the kitchen. 

He followed… how did Mutt get into the house when no one else could? He was curious, but also desperately wanted a new friend too. 

Black stormed over there banging on the door, but when Mutt answered he just stared at his brother as if his brother had grown a second head. 

“Sup?” Mutt asked nonchalantly.   
“DON’T YOU SUP ME MUTT. WHY ARE YOU HERE? HOW DID YOU GET IN? WHAT THE HELL IS GOING ON?”   
By the looks of it Black was more concerned than upset. Blue just looked curious. Looking behind him you didn’t flinch, so what you said held up. Everything you told him. That fact that you weren’t scared told him you weren’t lying. 

“S’kay if they come in?” Mutt asked you as you nodded your head. Stepping aside and letting them in he noticed that as soon as Blue was inside and bounded over to you you wrapped your arms around him and held him close even kissing the side of his cheek affectionately. 

Blue blushed his baby blue blush and Black stared… just what the hell was going on? 

“ANSWERS WENCH NOW!” 

“BLACK DON’T BE SO DEMANDING. I’M SURE SHE’LL TELL US IN HER OWN TIME.” 

You just smiled causing Black to gape at you as if you were off your rocker. Motioning for them to sit in the living room as went to fetch their favorites. 

/ /   
Leaving the house Black was a bit perplexed, but oddly… it made sense to him. Now he just felt bad. He did remember that time… Looking at Mutt as they all walked back after you once again isolated yourself from them and the outside world he sighed. He didn’t know what to do now… but it was like Mutt and him had been given a second chance. And this time their harsh world couldn’t fuck it up.


End file.
